Coronary artery disease remains the leading cause of morbidity and mortality in Western societies. Coronary artery disease is manifested in a number of ways. For example, disease of the coronary arteries can lead to insufficient blood flow to various areas of the heart. This can lead to the discomfort of angina and the risk of ischemia. In severe cases, acute blockage of coronary blood flow can result in irreversible damage to the myocardial tissue including myocardial infarction and the risk of death.
A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to merely treat the symptoms, with pharmaceuticals, or treat the underlying causes of the disease, with lifestyle modification. In more severe cases, the coronary blockage can be treated endovascularly or percutaneously using techniques such as balloon angioplasty, atherectomy, laser ablation, stents, and the like.
In cases where these approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft (CABG) procedure. CABG surgery, also known as “heart bypass” surgery, generally entails the use of a graft or conduit to bypass the coronary obstruction and, thereby provide blood flow to the downstream ischemic heart tissues. The major objective of any CABG procedure is to perform a technically perfect anastomosis of the graft with the vessel. Creation of a technically perfect anastomosis is generally complex, tedious, time consuming and its success is highly dependent on a surgeon's skill level.
The CABG procedure is typically conducted on an arrested heart while the patient is on a cardiopulmonary bypass (CPB) circuit, also known as a “heart-lung machine” that provides continuous systemic blood circulation, while cardioplegic cardiac arrest enables meticulous anastomosis suturing in a bloodless, still-heart, operating field. In a CPB procedure performed as an adjunct to a CABG procedure, the patient's venous blood that normally returns to the right atrium is diverted to a CPB system or circuit that supplies oxygen to the blood and removes carbon dioxide from the blood and returns the blood, at sufficient pressure, into the patient's aorta for further distribution through the arterial system to the body. Creation of the CPB circuit typically entails arterial and venous cannulation, connecting the bloodstream to a heart-lung machine, cooling the body to about 32° Celsius, cross clamping of the aorta, and cardioplegic perfusion of the coronary arteries to arrest and cool the heart to about 4° Celsius. The arrest or stoppage of the heart is generally required because the constant pumping motion of the beating heart would make surgery upon the heart difficult in some locations and extremely difficult if not impossible in other locations. Generally, such a CPB system requires several separate components, including an oxygenator, several pumps, a reservoir, a blood temperature control system, filters, and flow, pressure and temperature sensors.
A blood vessel or vessels for use in the graft procedure are harvested or mobilized from the patient. In the majority of patients, obstructed coronary arteries are bypassed using an in situ internal mammary artery (IMA) or a reversed segment of saphenous vein harvested from a leg although other graft vessels may also be used. For this reason, CABG surgery is typically performed through a median sternotomy, which provides access to the heart and to all major coronary branches. A median sternotomy incision begins just below the sternal notch and extends slightly below the xiphoid process. A sternal retractor is used to spread the left and right rib cage apart for optimal exposure of the heart. Hemostasis of the sternal edges is typically obtained using electrocautery with a ball-tip electrode and a thin layer of bone wax. The pericardial sac is opened thereby achieving direct access to the heart. One or more grafts are attached to the relevant portion of a coronary artery (or arteries) to bridge the obstruction while the heart is in cardiac arrest. Then, the patient is weaned from CPB, the heart is restarted, and cannulation is discontinued. The surgical incisions in the chest are then closed.
The CABG procedure is generally expensive, lengthy, traumatic and subject to patient risk. The arrest of the heart and the use of the CPB circuit add to the time and expense of the CABG procedure and present a number of risk factors to the patient. The initiation of global (hypothermic) cardiac arrest may result in global myocardial ischemia, and cross clamping the ascending aorta may contribute to the patient experiencing a post-operative stroke. In fact, recent studies have shown aortic clamping and manipulation may release atherosclerotic debris into the bloodstream, resulting in neurological injury. Exposure of blood to foreign surfaces results in the activation of virtually all the humoral and cellular components of the inflammatory response, as well as some of the slower reacting specific immune responses. A systemic inflammatory response can result due to the interactions of blood elements with the artificial material surfaces of the components of the CPB circuit. Other complications associated with cardiopulmonary bypass include loss of red blood cells and platelets due to shear stress damage. In addition, cardiopulmonary bypass requires the use of an anticoagulant, such as heparin that increases the risk of hemorrhage. Cardiopulmonary bypass also sometimes necessitates giving additional blood to the patient that may expose the patient to blood-borne diseases, if it is from a source other than the patient.
Therefore, a number of cardiac surgical procedures have been developed or proposed to enable off-pump, beating heart, CABG procedures either through a median sternotomy or employing minimally invasive procedures and even totally endoscopic procedures with access through ports extending through the chest wall into the thoracic cavity. For example, Trapp and Bisarya, in “Placement of Coronary Artery Bypass Graft Without Pump Oxygenator”, Annals Thorac. Surg., Vol. 19, No. 1, (January 1975), pp. 1-9, immobilized the area of the bypass graft by encircling sutures deep enough to incorporate enough muscle to suspend an area of the heart and prevent damage to the coronary artery. More recently, Fanning et al. also reported, in “Reoperative Coronary Artery Bypass Grafting Without Cardiopulmonary Bypass”, Annals Thorac. Surg., Vol. 55, (February 1993), pp. 486-489, immobilizing the area of the bypass graft with stabilization sutures.
Other approaches of stabilizing at least a portion of the heart to facilitate CABG or other procedures involve applying pressure against the heart wall as exemplified by the stabilization apparatus disclosed in U.S. Pat. Nos. 5,875,782, 6,120,436, and 6,331,158, for example. In one embodiment disclosed in the '436 patent, a U-shaped platform is pressed against the heart surface exposed through a thoracotomy and maintained there by suturing the platform to the myocardium or by attaching the platform to the end of an adjustable arm. The adjustable arm is mounted to a rib retractor maintaining the ribs spread apart, and the adjustable arm can be adjusted to direct pressure through the platform against the heart to stabilize it.
In addition, mechanical systems for lifting the heart, particularly to enable access to the heart for performing valve surgery, have been proposed as exemplified in the apparatus disclosed in U.S. Pat. No. 6,558,318.
In one embodiment disclosed therein, a tissue positioning tool is provided comprising a tool support member adapted to be mounted to the patient's body, an elongated shaft supported by the tool support member adapted to be passed through a small incision, and a tissue supporting member having a surface adapted to contact tissue, e.g., the heart, that can be attached and detached from the elongated shaft. In use, the tissue support member is introduced into the thoracic cavity through a first percutaneous penetration, and the elongated shaft is introduced through a second percutaneous penetration. The tissue-supporting member is connected to the shaft within the thoracic cavity to form a tissue-positioning tool. Assembling the tool within the thoracic cavity allows the use of tissue-engaging devices having parts and surfaces too large to be introduced through the typically smaller penetration from which the shaft of the tool extends.
These mechanical systems for applying force against or lifting the heart are less efficacious than systems that apply suction against the heart to engage the heart. Suction-assisted tissue-engaging devices, such as the various models of the Medtronic® Octopus 3™ tissue stabilizer and or Starfish™ heart positioner and accessories available from the assignee of the present invention, use suction for stabilizing or positioning, respectively, tissue of an organ. The Medtronic® Octopus 3™ tissue stabilizer is approved for use in applying suction to a surface of the heart to stabilize the heart tissue at the site of engagement while the heart is beating to facilitate a surgical procedure, e.g., to perform an anastomosis in the course of a CABG procedure. The Starfish™ heart positioner is approved for use in applying suction to a surface of the heart, particularly near the apex of the heart, to move and reposition the heart to achieve better access to areas that would otherwise be difficult to access, such as the posterior or backside of the heart. For example, the surgeon can bring an anastomosis site into better view by supporting and rotating the heart using the Starfish™ heart positioner. The surgeon can also use the Octopus 3™ tissue stabilizer in the same procedure to stabilize the anastomosis site. See, for example, commonly assigned U.S. Pat. Nos. 5,836,311, 5,927,284, 6,015,378, 6,464,629, and 6,471,644 and U.S. patent application Ser. No. 09/678,203, filed Oct. 2, 2000, and European Patent Publication No. EP 0 993 806 describing aspects of the Octopus 3™ heart stabilization system and commonly assigned U.S. Patent Application Publication US 2002/0095067 disclosing aspects of the Starfish™ heart positioner.
The Octopus 3™ tissue stabilizer employs a pair of elongated, malleable suction pads mounted to extend in a U-shape from the distal end of a malleable, articulating arm, and a tissue spreading mechanism that the surgeon can employ to spread the elongated arms apart. As described in the above-referenced '629 patent, after the suction pods are applied to the heart surface, tightening a cable extending through the arm fixes the arm in place. Then, the suction pods may be spread apart from each other to tighten the surface of the cardiac tissue lying between the suction pods. In one embodiment, fixation of the articulating arm as well as the spreading apart of the suction pods may occur concurrently or almost concurrently through the tensioning of a single cable.
The Starfish™ heart positioning system employs a three appendage, silicone head mounted to the distal end of a malleable, articulating arm. The silicone head is shaped so that the flexible appendages or legs diverge apart and can engage the heart surface particularly adjacent to the apex of the heart to lift and position the heart when suction is applied.
Further suction-assisted tissue-engaging devices for use in cardiac surgery through a sternotomy are disclosed in U.S. Pat. No. 5,799,661 in PCT Publication WO 01/17437 A2 wherein a conical or helmet shaped suction member is mounted to the distal end of an articulating arm and is adapted to apply suction to the apex of the heart and lift the heart. Other suction-assisted tissue-engaging devices for cardiac surgery having circular or horseshoe-shaped suction members introduced through a sternotomy are disclosed in U.S. Pat. Nos. 5,868,770, 5,782,746, and 6,071,295.
These suction-assisted, tissue-engaging devices are used in open chest sternotomy procedures that involve making a 20 to 25 cm incision in the chest of the patient, severing the sternum, cutting and peeling back various layers of tissue in order to give access to the heart and arterial sources, and fitting a retractor across the incision to maintain the ribs spread apart. The articulating arms of the above-described Medtronic® Octopus 3™ tissue stabilizer and or Starfish™ heart positioner are mounted to the Medtronic® OctoBase™ retractor.
Such median sternotomies are highly traumatic and typically require many sutures or staples to close the incision and 5 to 10 wire hooks to keep the severed sternum together during recovery. Such surgery often carries additional complications such as instability of the sternum, post-operative bleeding, and mediastinal infection. The thoracic muscle and ribs are also severely traumatized, and the healing process results in an unattractive scar. Post-operatively, most patients endure significant pain and must forego work or strenuous activity for a long recovery period.
Many minimally invasive surgical techniques and devices have been proposed or introduced in order to reduce the risk of morbidity, expense, trauma, patient mortality, infection, and other complications associated with open-chest cardiac surgery. Less traumatic limited open chest techniques using an abdominal (sub-xyphoid) approach or, alternatively, a “Chamberlain” incision (an approximately 8 cm incision at the sternocostal junction), have been developed to lessen the operating area and the associated complications. In recent years, a growing number of surgeons have begun performing coronary artery bypass graft (CABG) procedures using minimally invasive direct coronary artery bypass grafting (MIDCAB) surgical techniques and devices. Using the MIDCAB method, the heart typically is accessed through a mini-thoracotomy (i.e., a 6 to 8 cm incision in the patient's chest) that avoids the sternal splitting incision of conventional cardiac surgery. A MIDCAB technique for performing a CABG procedure is described in U.S. Pat. No. 5,875,782, for example.
Other minimally invasive, percutaneous, coronary surgical procedures have been proposed or introduced that employ multiple small trans-thoracic incisions to and through the pericardium, instruments advanced through the incisions, and a thoracoscope to view the accessed cardiac site while the procedure is performed as shown, for example, in U.S. Pat. Nos. 6,332,468, 5,464,447, and 5,716,392. As stated in the '468 patent, instruments advanced through the incisions can include electrosurgical tools, graspers, forceps, scalpels, electrocauteries, clip appliers, scissors, etc. Each incision is maintained open by insertion of a cannula or port through the incision so that the instruments can be advanced through the lumen of the cannula or port. If a trocar is used, a trocar rod is inserted into the trocar sleeve, and the sharpened tip of the trocar rod is advanced to puncture the abdomen or chest to create the incision into the thoracic cavity. The trocar rod is then withdrawn leaving the trocar sleeve in place so that a surgical instrument can be inserted into the thoracic cavity through the trocar sleeve lumen.
In such procedures, the surgeon can stop the heart by utilizing a series of internal catheters to stop blood flow through the aorta and to administer cardioplegia solution. The endoscopic approach typically also utilizes groin cannulation to establish CPB and an intra-aortic balloon catheter that functions as an internal aortic clamp by means of an expandable balloon at its distal end used to occlude blood flow in the ascending aorta. A full description of an example of one preferred endoscopic technique is found in U.S. Pat. No. 5,452,733, for example.
The above-described Medtronic® Octopus 3™ tissue stabilizer and or Starfish™ heart positioner are not sized and designed to fit through such a minimally invasive incision or the lumen of a cannula or port or trocar sleeve. The use of the an early version of an Octopus™ tissue stabilizer through a minimally invasive incision without CPB to stabilize a site of the beating heart is disclosed in one embodiment in commonly assigned U.S. Pat. Nos. 6,464,630 and 6,394,948, for example. In this embodiment, the tissue stabilizer employs a single elongated suction pod fixed at the distal end of an elongated shaft to extend substantially axially and to the elongated shaft. It is necessary to employ two such elongated shafts and suction pods to place the suction pads on either side of the heart surface to be stabilized. Consequently, it would be difficult to position two such elongated shafts and suction pads through a single minimally invasive incision of parallel incisions. Thus, the suggested approach offers little advantage over employing a single large incision or sternotomy.
A modification of the Octopus™ tissue stabilizer is suggested in the above-referenced commonly assigned pending application Ser. No. 09/678,203, wherein the two suction pods are supported fixed to the distal end of the tissue stabilizer in a manner that enables the suction pods to be collapsed into a small diameter to facilitate insertion through the lumen of a cannula or port or trocar sleeve.
Other methods and apparatus that are introduced through percutaneously placed ports or directly through small trans-thoracic incisions for accessing the pericardial space employ suction devices to grip the pericardium or epicardium as disclosed, for example, in U.S. Pat. Nos. 4,991,578, 5,336,252, 5,827,216, 5,868,770, 5,972,013, 6,080,175, and 6,231,518. The suction devices are typically configured like a catheter or tube having a single suction lumen and typically having a further instrument delivery lumen. The suction lumen terminates in a single suction lumen end opening through the device distal end in the '578, '252, '175, '770, and '013 patents and through the device sidewall in the '216 and '518 patents. Certain of these patents recite that the applied suction draws a “bleb,” i.e., a locally expanded region of the pericardium, into the suction lumen or a suction chamber at the device distal end. A needle can then be advanced into the bleb and used to draw off fluids or deliver drugs into the pericardial space, or the like. In addition, it is suggested in these patents that treatment devices including catheters, guidewires, and electrodes, e.g., defibrillation electrodes, can be advanced into the pericardial space through a device introduction lumen for a variety of reasons. Although theoretically plausible, the ability to reliably maintain a vacuum seal against the pericardium when such treatment devices are advanced can be problematic.
Surgeons have found that the Octopus 3™ stabilization system and Starfish™ heart positioner provide significant benefits in the above-described operative procedures involving relatively large sternotomies or thoracotomies. It would be desirable to be able to enjoy the advantages of such suction-assisted tissue-manipulation systems using minimally invasive procedures for performing coronary procedures or to access and perform a procedure on other body tissue.